Add support for columns defined with "CHARACTER SET OCTETS"

For CHAR/VARCHAR columns, if the associated XSQLVAR has "sqlsubtype"
set to 1, this means the column was defined with "CHARACTER SET
OCTETS".

As OCTETS are raw binary data, convert these values into hexadecimal
representation, to match what isql does.

It may be desirable to add a connection-level option to return the
raw bytes, but there doesn't seem much point at the moment.

CHANGELOG

@@ -1,5 +1,8 @@
 Revision history for libfq
 
+0.6.0	2023-??-??
+	- support columns defined with "CHARACTER SET OCTETS"
+
 0.5.0	2022-12-28
 	- Add functions FQprepare() and FQexecPrepared()
 	- Handle errors encountered when executing isc_dsql_fetch()

src/libfq.c

@@ -84,6 +84,9 @@ static int _FQdspstrlen_line(FQresTupleAtt *att, short encoding_id);
 static int check_tuple_field_number(const FBresult *res,
 									int row_number, int column_number);
 
+
+static char *_FQformatOctet(char *data, int len);
+
 /* keep this in same order as FQexecStatusType in libfq.h */
 char *const fbresStatus[] = {
 	"FBRES_NO_ACTION",
@@ -3346,7 +3349,6 @@ _FQformatDatum(FBconn *conn, FQresTupleAttDesc *att_desc, XSQLVAR *var)
 	FQresTupleAtt *tuple_att;
 	short		   datatype;
 	char		  *p;
-	VARY2		  *vary2;
 	struct tm	   times;
 	char		   format_buffer[1024];
 	char		   pad_buffer[1024];
@@ -3373,20 +3375,38 @@ _FQformatDatum(FBconn *conn, FQresTupleAttDesc *att_desc, XSQLVAR *var)
 	switch (datatype)
 	{
 		case SQL_TEXT:
-			p = (char *)malloc(var->sqllen + 1);
 
-			memcpy(p, var->sqldata, var->sqllen);
-			p[var->sqllen] = '\0';
+			if (var->sqlsubtype == 1)
+			{
+				/* column defined as "CHARACTER SET OCTETS" */
+				p = _FQformatOctet(var->sqldata, var->sqllen);
+			}
+			else
+			{
+				p = (char *)malloc(var->sqllen + 1);
+
+				memcpy(p, var->sqldata, var->sqllen);
+				p[var->sqllen] = '\0';
+			}
 			break;
 
 		case SQL_VARYING:
-			vary2 = (VARY2*)var->sqldata;
-			p = (char *)malloc(vary2->vary_length + 1);
-			memcpy(p, vary2->vary_string, vary2->vary_length + 1);
-			p[vary2->vary_length] = '\0';
+		{
+			VARY2		  *vary2 = (VARY2*)var->sqldata;
 
+			if (var->sqlsubtype == 1)
+			{
+				/* column defined as "CHARACTER SET OCTETS" */
+				p = _FQformatOctet(vary2->vary_string, vary2->vary_length);
+			}
+			else
+			{
+				p = (char *)malloc(vary2->vary_length + 1);
+				memcpy(p, vary2->vary_string, vary2->vary_length + 1);
+				p[vary2->vary_length] = '\0';
+			}
+		}
 			break;
-
 		case SQL_SHORT:
 		case SQL_LONG:
 		case SQL_INT64:
@@ -3724,6 +3744,41 @@ _FQformatDatum(FBconn *conn, FQresTupleAttDesc *att_desc, XSQLVAR *var)
 }
 
 
+/**
+ * _FQformatOctet
+ *
+ * Display an octet string as hex values in upper case.
+ */
+static char *
+_FQformatOctet(char *data, int len)
+{
+	int i;
+	char *p, *q;
+
+
+	p = (char *)malloc((len * 2) + 1);
+	q = p;
+
+	for (i = 0; i < len; i++)
+	{
+		if (data[i])
+		{
+
+			sprintf(q, "%02X", (unsigned int)(data[i] & 0xFF));
+			q += 2;
+		}
+		else
+		{
+			sprintf(q, "00");
+			q += 2;
+		}
+
+	}
+
+	return p;
+}
+
+
 /**
  * FQformatDbKey()
  *